Ambrosia beetle threatening California trees

The ambrosia beetle bores into the trees and spreads a fungus that, in turn, attacks the vascular tissue of the tree and disrupts water and nutrient flow. The beetle also attacks Coast Live Oak, Box Elders and other trees.

Iqbal Pittalwala, UC Riverside | Aug 14, 2012

An ambrosia beetle named Polyphagous Shot Hole Borer is an invasive pest that attacks oak and avocado trees, causing branch dieback and eventually death. The beetle bores into the trees and spreads a fungus that, in turn, attacks the vascular tissue of the tree and disrupts water and nutrient flow. The beetle also attacks Coast Live Oak, Box Elders and other trees.

Both the fungus and the beetle were discovered on several backyard avocado trees in residential neighborhoods and a commercial avocado grove in Los Angeles County in February and March 2012. (The beetle was previously misidentified as the Tea Shot Hole Borer. But subsequent DNA sequencing at the University of California, Riverside revealed the beetle to be different from the Tea Shot Hole Borer. The name Polyphagous Shot Hole Borer has been suggested for the beetle.) No effective solutions for eradicating the beetle have been found.

Scientists from the United States and abroad are meeting on Aug. 12-14, 2012, in Riverside, Calif., to discuss the beetle, its biology, the fungus it spreads, and strategies to effectively monitor and control the pest.

The public is invited to attend the free open session of the three-day meeting from 2 p.m. to 5 p.m. on Tuesday, Aug. 14, at the Marriott Riverside Hotel, 3400 Market St., Riverside, Calif. At the public meeting, the scientists will address the new beetle/fungus complex and explain what problem it poses, the extent of the problem in California, what detection and control measures are currently available, and how Israel is dealing with the same pest. A Q&A period is scheduled for 4:25 p.m.

Ambrosia beetles typically live symbiotically with one or more fungi, which they spread into trees when they bore into the tree’s tissue. When dieback begins, its symptoms include a white powdery exudate[2] (either dry or surrounded by wet discoloration of the outer bark) around beetle entry holes in the bark.

The panelists at the open session are UC Riverside’s Mary Lu Arpaia, a Cooperative Extension subtropical horticulturalist; Akif Eskalen, an extension plant pathologist; Mark Hoddle, the director of the Center for Invasive Species Research; Timothy Paine, a professor of entomology; and Richard Stouthamer, also a professor of entomology. They will be joined by Zvi Mendel of the Agricultural Research Organization, Israel; Donald Hodel, an environmental horticulturist for the University of California Cooperative Extension, Los Angeles County; Tom Roberts of the pest management industry; and Tom Coleman of the U.S. Department of Agriculture Forest Service.

Parking at the Marriott Riverside costs $4. Members of the public are advised to register their attendance by emailing [email protected][3]. Seating is open and limited.